From e6fe8a7d53a35d3efcf85dba120db9143b84e2f6 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Sat, 6 Feb 2021 17:48:26 +0100
Subject: [PATCH] Handle errors gracefully, in
 `PartialEvaluator.translateFont`, when fetching the font file (issue 9462)

The *third* page of the referenced PDF document currently fails to render completely, since one of its font files fail to load.
Since that error isn't handled, a large part of the text is thus missing which looks quite bad. By "replacing" the font data with an *empty* stream, we'll thus be able to fallback to rendering the text with a standard font (instead of using `ErrorFont`). While there's obviously no guarantee that things will look perfect, actually rendering the text at all should be an improvement in general.

Also, print a warning in `PartialEvaluator.loadFont` when the `PartialEvaluator.translateFont` method rejects, since that'd have helped debug/fix the issue faster.
---
 src/core/evaluator.js | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/core/evaluator.js b/src/core/evaluator.js
index cfcc77feb..cbc2e94d5 100644
--- a/src/core/evaluator.js
+++ b/src/core/evaluator.js
@@ -47,6 +47,7 @@ import {
   Ref,
   RefSet,
 } from "./primitives.js";
+import { DecodeStream, NullStream } from "./stream.js";
 import {
   ErrorFont,
   Font,
@@ -85,7 +86,6 @@ import {
 } from "./image_utils.js";
 import { bidi } from "./bidi.js";
 import { ColorSpace } from "./colorspace.js";
-import { DecodeStream } from "./stream.js";
 import { getGlyphsUnicode } from "./glyphlist.js";
 import { getMetrics } from "./metrics.js";
 import { MurmurHash3_64 } from "./murmurhash3.js";
@@ -1066,7 +1066,7 @@ class PartialEvaluator {
     try {
       preEvaluatedFont = this.preEvaluateFont(font);
     } catch (reason) {
-      warn(`loadFont - ignoring preEvaluateFont errors: "${reason}".`);
+      warn(`loadFont - preEvaluateFont failed: "${reason}".`);
       return errorFont();
     }
     const { descriptor, hash } = preEvaluatedFont;
@@ -1156,6 +1156,7 @@ class PartialEvaluator {
         this.handler.send("UnsupportedFeature", {
           featureId: UNSUPPORTED_FEATURES.errorFontTranslate,
         });
+        warn(`loadFont - translateFont failed: "${reason}".`);
 
         try {
           // error, but it's still nice to have font type reported
@@ -3459,7 +3460,16 @@ class PartialEvaluator {
       throw new FormatError("invalid font name");
     }
 
-    var fontFile = descriptor.get("FontFile", "FontFile2", "FontFile3");
+    let fontFile;
+    try {
+      fontFile = descriptor.get("FontFile", "FontFile2", "FontFile3");
+    } catch (ex) {
+      if (!this.options.ignoreErrors) {
+        throw ex;
+      }
+      warn(`translateFont - fetching "${fontName.name}" font file: "${ex}".`);
+      fontFile = new NullStream();
+    }
     if (fontFile) {
       if (fontFile.dict) {
         var subtype = fontFile.dict.get("Subtype");